Add PR template format gate (#3412)

* Add PR template format gate

* Address CodeRabbit PR template gate feedback

scripts/pr-template-policy.cjs

@@ -0,0 +1,167 @@
+#!/usr/bin/env node
+
+const TRUSTED_AUTHOR_ASSOCIATIONS = new Set([
+  'CONTRIBUTOR',
+  'COLLABORATOR',
+  'MEMBER',
+  'OWNER',
+]);
+
+const DEFAULT_TEMPLATE_MARKERS = [
+  'Wrong template',
+  'Every PR must use a typed template',
+  'Select the template that matches your PR',
+];
+
+const TEMPLATES = [
+  {
+    name: 'fix',
+    heading: 'Fix PR',
+    requiredHeadings: [
+      'Fix PR',
+      'Linked Issue',
+      'What was broken',
+      'What this fix does',
+      'Testing',
+      'Checklist',
+    ],
+  },
+  {
+    name: 'enhancement',
+    heading: 'Enhancement PR',
+    requiredHeadings: [
+      'Enhancement PR',
+      'Linked Issue',
+      'What this enhancement improves',
+      'Before / After',
+      'How it was implemented',
+      'Testing',
+      'Scope confirmation',
+      'Checklist',
+    ],
+  },
+  {
+    name: 'feature',
+    heading: 'Feature PR',
+    requiredHeadings: [
+      'Feature PR',
+      'Linked Issue',
+      'Feature summary',
+      'What changed',
+      'Implementation notes',
+      'Spec compliance',
+      'Testing',
+      'Scope confirmation',
+      'Checklist',
+    ],
+  },
+];
+
+function stripMarkdownDecoration(value) {
+  return value
+    .replace(/^\s*#+\s*/, '')
+    .replace(/\s*#+\s*$/, '')
+    .replace(/\*\*/g, '')
+    .trim()
+    .toLowerCase();
+}
+
+function extractHeadings(body) {
+  const headings = new Set();
+  for (const line of String(body || '').split(/\r?\n/)) {
+    if (/^\s*#{1,6}\s+\S/.test(line)) {
+      headings.add(stripMarkdownDecoration(line));
+    }
+  }
+  return headings;
+}
+
+function includesDefaultTemplate(body) {
+  const text = String(body || '').toLowerCase();
+  return DEFAULT_TEMPLATE_MARKERS.some((marker) => text.includes(marker.toLowerCase()));
+}
+
+function matchingTemplate(body) {
+  const headings = extractHeadings(body);
+  for (const template of TEMPLATES) {
+    if (!headings.has(stripMarkdownDecoration(template.heading))) continue;
+    const missingHeadings = template.requiredHeadings.filter((heading) => {
+      return !headings.has(stripMarkdownDecoration(heading));
+    });
+    return {
+      template: template.name,
+      missingHeadings,
+    };
+  }
+  return {
+    template: null,
+    missingHeadings: [],
+  };
+}
+
+function evaluatePrTemplate(body, authorAssociation) {
+  const association = String(authorAssociation || '').toUpperCase();
+  const trusted = TRUSTED_AUTHOR_ASSOCIATIONS.has(association);
+  const normalizedBody = String(body || '').trim();
+
+  let valid = true;
+  let reason = 'PR body uses a typed pull request template.';
+  let template = null;
+  let missingHeadings = [];
+
+  if (!normalizedBody) {
+    valid = false;
+    reason = 'PR body is empty; a typed pull request template is required.';
+  } else if (includesDefaultTemplate(normalizedBody)) {
+    valid = false;
+    reason = 'PR body still contains the default wrong-template guidance.';
+  } else {
+    const match = matchingTemplate(normalizedBody);
+    template = match.template;
+    missingHeadings = match.missingHeadings;
+    if (!template) {
+      valid = false;
+      reason = 'PR body does not match the fix, enhancement, or feature template.';
+    } else if (missingHeadings.length > 0) {
+      valid = false;
+      reason = `PR body appears to use the ${template} template but is missing required headings.`;
+    }
+  }
+
+  let action = 'pass';
+  if (!valid) {
+    action = trusted ? 'warn' : 'close';
+  }
+
+  return {
+    valid,
+    action,
+    trusted,
+    authorAssociation: association || 'UNKNOWN',
+    template,
+    reason,
+    missingHeadings,
+  };
+}
+
+function main() {
+  const result = evaluatePrTemplate(process.env.PR_BODY || '', process.env.AUTHOR_ASSOCIATION || '');
+  process.stdout.write(`${JSON.stringify(result)}\n`);
+  if (process.env.GITHUB_OUTPUT) {
+    const fs = require('fs');
+    fs.appendFileSync(process.env.GITHUB_OUTPUT, `result=${JSON.stringify(result)}\n`);
+    fs.appendFileSync(process.env.GITHUB_OUTPUT, `action=${result.action}\n`);
+    fs.appendFileSync(process.env.GITHUB_OUTPUT, `valid=${result.valid ? 'true' : 'false'}\n`);
+  }
+}
+
+if (require.main === module) {
+  main();
+}
+
+module.exports = {
+  evaluatePrTemplate,
+  extractHeadings,
+  includesDefaultTemplate,
+  matchingTemplate,
+};